1. Field of the Invention
The present invention relates generally to a system for establishing and managing a multimedia Push To Talk (PTT) over Cellular (PoC) session for performing a multimedia call service, a method thereof, and a User Equipment (UE) therefor, and in particular, to a system for establishing a PoC session supporting only media types supported by at least one receivable PoC client in the PoC session when various media types supported by PoC clients are not common in PoC session establishment or when transportable media types contained in a first response message are different from media types provided by a sender, a method thereof, and a UE therefor.
2. Description of the Related Art
The significant development of mobile communication and the spread of communication networks have contributed to various extra services and applications using a cellular phone. At the same time, demand among cellular phone users for various extra services, such as a positioning service, a multimedia service, and a Push-To-Talk (PTT) service, is increasing. Among these extra services, the PTT service supports various supplementary functions such as an instant messenger function and a status display function, as well as a group call and a voice call which are also provided by an existing radio or a Trunked Radio System (TRS).
Currently, standardization of a PTT-over-Cellular (PoC) service which employs the PTT function in a mobile communication network is actively being developed. One unique feature of the PoC service, which is distinguished from existing mobile communication services, is that a user can participate in a plurality of PoC sessions and can move among the PoC sessions to use a call service. A requirement that the user can move among the plurality of PoC sessions to use the call service is specified in the Open Mobile Alliance (OMA) which is a forum for specifying mobile communications services.
Meanwhile, a PoC V 2.0 system supports a PoC multimedia call service. In order to support the PoC multimedia call service, the PoC V 2.0 system defines video, images, and text as new multimedia types as well as sound.
Current PoC systems can display multiple streams, such as video and/or images, due to performance improvement of User Equipments (UEs).
As described above, if the PoC V 2.0 system uses a conventional PoC V 1.0 session establishment method and system, various multimedia services supported by the PoC V 2.0 system may be limited, and a session establishment time takes long.